1. Field of Invention
The present invention relates to a compact power module for generating impulses of high current for driving electric motors to create impulse torque in short duration, thereby energizing hand-held tools, igniting combustion engines, or actuating automatic systems. More specifically, the present invention relates to a switching capacitor without moving parts wherein supercapacitors, ultracapacitors, or electric double layer capacitors are configured from parallel connection during charging phase to series connection at the time of use by electromagnetic switching elements to discharge for generating the desired impulses.
2. Description of Related Art
Impulse energy is very useful in numerous industries. For example, it can be used for crushing stones (U.S. Pat. No. 6,058,029), for vaporizing metal (U.S. Pat. No. 5,359,279), for removing pollutant particles (U.S. Pat. No. 4,162,417), and for collecting blood sample (U.S. Pat. No. 5,839,446).
Many techniques can be used to generate impulse energy, for example, seawater and membrane used in submarine torpedo launch systems for producing a high velocity fluid flow in a very short duration (U.S. Pat. Nos. 5,200,572 and 6,146,114). High energy pulses can also be generated by using acoustic transducer (U.S. Pat. No. 4,541,081), piezoelectric transducer (U.S. Pat. No. 6,204,592) and flywheel (U.S. Pat. No. 5,511,715). Nevertheless, impulse energy is most commonly generated using electrical circuitry as in U.S. Pat. Nos. 4,258,405; 4,994,160; 5,359,279; 5,729,562; 5,895,584; 6,058,029; 6,063,168 and 6,359,424. Though capacitor is universally included in the prior art electric impulse generators, various semiconductor switching devices, such as, thyratron, thyristor, IGBT or SCR, as well as coil, transformer and microcontroller of pulse width modulation (PWM) are employed for switching the capacitor. Because of the chip count in the prior art electric impulse generators is high, the resultant electrical arrangements are thus bulky and costly. Moreover, thyratron has a lifetime problem associated with cathode and anode erosion that can reduce switching efficiency and voltage hold-off ability of the semiconductor element.
Impulse force is also required for operating portable hand held tools including stapler, nailer, tacker, drill, hammer, pinner, breaker, nibbler, compactor, hedger, trimmer, and pruner, etc. Taking nailer or stapler as an example, it is conventionally pneumatically powered by compressed air (U.S. Pat. No. 6,155,472) or by pressurized fuel gas (U.S. Pat. No. 5,911,350) to charge the spring to a compressed position for driving a nail into wood or concrete surface. The aforementioned tools hence need a job site compressor or a combustion chamber that impairs the mobility of the tools. To bestow the portable tools the highest mobility, the tools should have no string attached thereto or be cordless, and preferably, the tools are powered by batteries. Similar to AC powered tools, the DC powered tools utilize solenoid actuators in driven applications as well. In U.S. Pat. No. 5,105,329 issued to Goldner, which is included herein by reference, a solid-state circuitry is provided for driving the armature of a battery operated electric stapler. As batteries are the sole power source for a DC stapler, the effective operating lifetime of batteries is addressed by xe2x80x9c329 by means of a complex circuit using a number of electronic components. Nowadays, many commercial cordless power tools rely at first on NiCd batteries and then switch to NiMH batteries on environmental cause for driving the electric motors of tools. However, batteries are limited to their power densities that they are unable to deliver the required impulse torque for heavy-duty jobs, or the effective use-time of batteries is reduced due to overdraft of power. This invention provides a cost-effective method using supercapacitors and electromagnetic relays to solve the foregoing problems related to the electric impulses generation.
The present invention utilizes supercapacitors as load leveling for batteries in DC powered devices. Therefore, the number of batteries required for powering the devices can be reduced, or the effective operating time of batteries can be prolonged. When alkaline batteries are employed in the power units of DC powered devices, no wait time is required for charging batteries so that the devices can perform immediately.
The present invention uses a minimum number of batteries, but sufficient to charge the supercapacitors. When the loads demand large currents, the supercapacitors will promptly supply the required power, leaving batteries isolated or under a condition of low discharge rate.
The present invention uses only electromagnetic relays as the switching element to switch the supercapacitors from parallel connection to series connection for delivering electric impulses. The relays are small and inexpensive. Thereby, the impulse generator consisting of supercapacitors and relays is compact and cost-effective.
The present invention controls the capacitance and ESR (equivalent series resistance) of the supercapacitors so that the magnitude of impulse force (or impulse torque) provided by the generator is tailor-made.
These and other features, objectives as well as advantages in accordance with the present invention will become apparent from the following detailed description, and from preferred embodiments with the accompanying drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.